The Conservative Party leadership battle was set to turn nasty today as all five contenders continued to slug it out.

Former Chancellor Kenneth Clarke has been rolling round Blackpool like a Chieftain tank firing rounds at both rivals and the Labour government.

In his big conference address this afternoon he was staking his claim to the Conservative crown by telling delegates that only he has the political firepower to take on Tony Blair and Gordon Brown.

Mr Clarke's battle plan is based largely on the belief that alone among the five contenders, he will be a popular choice with the public - even if much of his own party dislike his views on Europe, the economy and public services.

But he said: "If you think I have gone through all this process to try and become Prime Minster in four years' time to see the whole blasted thing exploded when I destroy my political base by trying to take us into the single currency, I can only assure you that is a paranoid fear."

But first up on the conference catwalk to woo Tory activists was to be Shadow Education Secretary David Cameron. At 38 he is regarded as a young blood in the Conservative Party and far younger than Clarke who will be pushing 70 by the next election.

Repeating his call for Tories to "change and modernise our culture and attitudes and identity", the shadow education secretary said: "What I'm talking about is fundamental change, so that when we fight the next election street by street, house by house, flat by flat we have a message that is relevant to people's lives today."

Tomorrow it will be the turn of bookies' favourite Shadow Home Secretary David Davis - already assured of a place in the run-off for the final vote and former party chairman Liam Fox.

The fifth candidate, former Foreign Secretary Sir Malcolm Rifkind also warned his party conference it must change or whither away.